Synthetic penicillin and salts thereof



United States Patent O bolt Rolinson, Flat 3, Brockham Park, Betchworth, England No Drawing. Filed July 13, 1959, Ser. No. 826,492 Claims priority, application Great Britain June 9, 1959 7 Claims. (Cl. 260-2391) This invention relates to new synthetic compounds of value as antibacterial agents, as nutritional supplements in animal feeds, as agents for the treatment of mastitis in cattle and as therapeutic agents in poultry and animals, including man, in the treatment especially of infectious diseases caused by Gram-positive bacteria and, more partlcularly, relates to 6-(a-haloalkanoylamido)penicillanic acids and nontoxic salts thereof.

This application is a continuation-in-part of our prior, copending application S.N. 750,075, filed July 22, 1958, issued June 21, 1960, as US. Patent 2,941,995.

Antibacterial agents such as benzylpenicillin have proved highly effective in the past in the therapy of infections due to Gram-positive bacteria but such agents suf fer from the serious drawbacks of being unstable in aqueous acid, e.g. upon oral administration, and of being ineffective against numerous so-called resistant strains of bacteria, e.g. penicillin-resistant strains of Staphylococcus aureus (Microcococcus pyogenes var. aureus). In addition, benzylpenicillin is not an effective agent against many bacteria which produce penicillinase. Many of the compounds of the present invention, in addition to their potent antibacterial activity, exhibit resistance to destruction by acid or by penicillinase or are effective against benzylpenicillin-resistant strains of bacteria or inhibit benzylpenicillinase and thus potentiate the action of benzylpenicillin when admixed therewith.

There is provided, according to the present invention, a member selected from the group consisting of an acid having the formula wherein X represents halogen, Y represents a member selected from the group consisting of hydrogen and halogen and R represents amember selected from the group consistingof hydrogen and alkyl containing one to twenty carbon atoms inclusive (and including both straight chain, branched chain, saturated and unsaturated aliphatic groups); and nontoxic salts thereof, including nontoxic metallic salts such as sodium, potassium, calcium and aluminum, the ammonium salt and substituted ammonium salts, eg. salts of such nontoxic amines as trialkylamines, including triethylamine, procaine, dibenzylamine, N-benzyl-beta-phenethylamine, l-ephenamine, N,N'-dibenzylethylenediamine, dehydroabietylamine, N,N'-bis-dehydroabietylethylenediamine, and other amines which have been used to form salts with benzylpenicillin. Also included within the scope of the present invention are easily hydrolyzed esters which are converted to the free acid form by chemical or enzymatic hydrolysis. The-preferred halogen groups are chloro and bromo. The preferred series is that in which Y is hydro gen, R is hydrogen or alkyl and X is chloro.

The products of the present invention are prepared by reaction of 6-aminopenicillanic acid, preferably in the form of a neutral salt such as the sodium salt or the tri- 3,025,290 Patented Mar. 13, p 1962 ethylamine salt, with an acid chloride having the formula x o R-(:3-( i-Cl wherein R, X and Y have the meaning set forth above, or its functional equivalent as an acylating' agent for'a primary amino group. Such equivalents include the corresponding carboxylic acid bromides, acid anhydrides and mixed anhydrides with other carboxylic acids, including monoesters, and particularly lower aliphatic esters, of carbonic acid.

'Thus, an elegant procedure for preparing a compound of the present invention by Way of a mixed anhydride with ethoxyor isobutoxy-carbonic acid comprises mixing 0.01 mole of an acid (whose acid chloride is set forth above), 0.01 mole isobutyl chloroformate and 0.011 mole tertiary hydrocarbonyl or aliphatic amine such as triethylamine in an anhydrous, inert and preferably water-miscible solvent such as p-dioxane (e.g. 20 ml.) and if desired 2 ml. pure, dry acetone for about thirty minutes in the cold, e.g. at about 4 C. To this solution of the mixed anhydride there is then added a chilled solution of 0.01 mole 6-amino penicillanic acid and 0.01 mole tertiary hydrocarbonyl amine, e.g. triethylamine, in, for example, 20 ml. of a solvent such as water. The reaction mixture is stirred for a period of an hour or so to form thesubstituted ammonium salt of the desired product. The mixture may then, if desired, be extracted at alkaline pH (such as pH 8; aqueous sodium bicarbonate maybe used, for example, if necessary to adjust the pH) with a waterimmiscible solvent such as ether to remove unreacted starting materials. The product in the aqueous phase is then converted to the free acid, preferably in the cold under a layer of ether by the addition of dilute mineral acid, e.g. 5NH SO to pH 2. The free acid is then extracted into a water-immiscible, neutral organic solvent such as ether and the extract is washed with water quickly in the cold, if desired, and then dried, as with anhydrous Na SO The product in the ethereal extract in its free acid form is then converted to any desired metal or amine salt by treatment with the appropriate base, e.g. a free amine such as procaine base or a solution of potassium 2-ethylhexanoate in dry n-butanol. These salts are usually insoluble in solvents such as ether and can be recovered in pure form by simple filtration. Another method of preparing an ethereal solution of the acid form of a compound of the present invention comprises preparing a solution in 20 ml. water of 0.00463 mole 6-aminopenicillanic acid and 1.56 gm. sodium bicarbonate, adding 0.00476 mole of an acid chloride whose'formula is set forth above and shaking vigorously at room temperature, e.g. for twenty to sixty minutes. The mixture is then extracted with ether to remove unreacted or hydrolyzed starting materials. The solution is then acidified (preferably in the cold) to pH 2, as with dilute sulfuric acid, and the, free acid form of the prodnet is extracted into ether (e.g., two portions of 25 ml.). This ethereal extract is dried, as with anhydrous sodium sulfate, and the drying agent is removed to leave a dry ethereal solution from which the product is easily iso lated, preferably in the form of an ether-insoluble salt such as the potassium salt. This procedure is used when the acid chloride reacts with a primary amine more rapidly than'it does with water, as determined by simple test. In this procedure the acid chloride may be replaced by equimolar amount of the corresponding acid bromide or acid anhydride.

Since some of the antibiotic substances obtained by the process of this invention are relatively unstable compounds which readily undergo chemical changes resulting in the loss of an antibiotic activity, it is desirable to choose reaction conditions which are sufficiently moderate to avoid their decomposition. The reaction conditions chosen will, of course, depend largely upon the reactivity of the chemical reagent being used. ,In most instances, a compromise has to be made between the use of very mild conditions for a lengthy period and the use of more vigorous conditions for a shorter time with the possibility of decomposing some of the antibiotic substance.

The temperature chosen for the process of preparation of the derivatives of penicillanic acid should in general not exceed 30 C. and in many cases a suitable temperature is ambient temperature. Since the use of strongly acid or alkaline conditions in the process of this invention should be avoided, it has been found preferable to perform the process at a pH of from 6 to 9, and this can conveniently be achieved by using a buffer, for example a solution of sodium bicarbonate, or a sodium phosphate buffer. In addition to the use of aqueous media for the reaction, including filtered fermentation broths or aqueous solutions of crude 6-aminopenicillanic acid, use can be made of organic solvents which do not contain reactive hydrogen atoms. Examples of such inert solvents are dimethylformamide, dimethylacetamide, chloroform, acetone, methyl isobutyl ketone and dioxane. Frequently it is highly satisfactory to add an aqueous solution of a salt of 6-aminopenicillanic acid to a solution of the acylating agent in an inert solvent and preferably in an inert solvent which is miscible with water, such as acetone or dimethylfo-rmamide. Vigorous stirring is, of course, advisable when more than one phase is present, e.g. solid and liquid or two liquid phases.

At the conclusion of the reaction, the products are isolated if desired by the techniques used with benzylpenicillin and phenoxymethylpenicillin. Thus, the product can be extracted into diethyl ether or n-butanol at acid pH and then recovered by lyophilization or by conversion to a solvent-insoluble salt, as by neutralization wit-h an n-butanol solution of potassium 2-ethylhexanoate, or the product can be precipitated from aqueous solution as a water-insoluble salt of an amine or recovered directly by lyophilization, preferably in the form of a sodium or potassium salt. When formed as the triethylamine salt, the product is converted to the free acid form and thence to other salts in the manner used with benzylpenicillin and other penicillins. Thus, treatment of such a triethylamine compound in water with sodium hydroxide converts it to the sodium salt and the t-riethylamine may be removed by extraction, as with toluene. Treatment of the sodium salt with strong aqueous acid converts the compound to the acid form, which can be converted to other amine salts, e.g., procaine, by reaction with the amine base. Salts so formed are isolated by lyophilization or, if the product is insoluble, by filtration. A particularly elegant method of isolating the product as a crystalline potassium salt comprises extracting the product from an acidic aqueous solution (e.g. pH 2) into diethyl ether, drying the ether and' adding at least one equivalent of a solution of potassium 2-ethylhexanoate (e.g. 0.373 gm./ml.) in dry n-butanol. The potassium salt forms, precipitates, usually in crystalline form, and is collected by filtration or decantation.

When an acid chloride, an acid bromide or an acid anhydride is used in a process of the present invention,

'it is prepared from the corresponding acid according to the techniques set forth in the literature for use with a-chloroacetic acid or alpha-chloropropionic acid. In the few instances where the u-haloalkanoic acid may not have been described, it is prepared from the corresponding alkanoic acid by chlorination by direct bromination in the presence of P01 (Marvel, Organic Syntheses, 20, 106; 21, 71) or from the corresponding alkanoic acid chloride or acid by direct chlorination using PCl or I; as a catalyst [A. Galat, J. Amer. Chem. Soc. 69,

86 (1947)] or from the appropriate malonic acid by chlorination with SO CI or C1 followed by monodecarboxylation with heat or by treatment of an hydroxy ester with POCI in the presence of pyridine [Helv. Chim. Acta., 12, 63 (1929); C. Wegand, Organic Preparations, page 99] or by halogen exchange between esters of the corresponding alpha-chloro or alpha-bromo acids and excess potassium fluoride in dirnethylformamide.

6-Aminopenicillanic acid is prepared according to Batchelor et al. (Nature 183, 257, 258, January 24, 1949) or Belgian Patent 569,728. It is used in the above reactions as the salt of a metal or a tertiary hydrocarbonyl amine or as an mter of a hydrocarbonyl alcohol.

Hydrocarbonyl alcohols and tertiary hydrocarbonyl amines are compounds having the formulae wherein the R groups contain only the elements carbon and hydrogen.

PREPARATION OF 6-AMINOPENICILLANIC ACID As set forth in our prior, copending application S. N. 750, 075, filed July 22, 1958, of which this application is a continuation-in-part, the intermediate 6-aminopenicillanic acid is isolated after removal of the natural penicillins from penicillin fermentation broths prepared without the use of added precursors such as phenylacetic acid. For this purpose, suitable penicillin-producing moulds include species of Penicillium, for example Penicillium chrysogenum 5120C, and the members of the notatumchrysogenum group. The mould is grown preferably unde aerobic submerged conditions. The culture medium used can be one of the generally accepted media commonly used in the preparation of penicillins. The culture medium usually consists essentially of a carbohydrate nutrient material, for example glucose or lactose; calcium carbonate, sodium sulphate, and a nitrogenous material capable of providing the nitrogen necessary for the growth of the mould. The nitrogenous material can be either a natural substance, for example peanut meal, or it can be one or more chemical compounds containing nitrogen, for example ammonium salts such as ammonium lactate or ammonium acetate. Where one or more chemical compounds are used as the nitrogenous material it is usual to incorporate in the culture medium very small amounts of a number of metals such as calcium, iron, zinc, copper, magnesium and manganese and these are normally introduced in the form of an aqueou solution of their salts. A suitable culture medium containing the ammonium salts as the nitrogenous material is described by Jarvis and Johnson, J.A.C.S., 69, 3010 (1947), and J. Bact. 59, 51 (1950). Natural nitrogenous materials such as peanut meal usually contain sufiicient amounts of suitable inorganic salts andthus when such materials are used in the culture medium it is usually not necessary to make a separate addition of inorganic salts.

The fermentation conditions used in the preparation of the fermentation liquor used in this invention can vary between wide limits, but it has been found preferable to use conditions similar to those commonly used in the preparation of Penicillin G. The temperature employed is preferably one from 20 C. to 35 C. and very satisfactory results have been obtained using a temperature of 2527 C. The time required for the fermentation depends upon the culture medium andthe mould used .and the temperature at which the fermentation is carried achieved by shaking the fermentation mixture on a rotary shaking machine. When working on a larger scale, aerobic conditions can conveniently be obtained either by bubbling air or oxygen through the fermentation mixture, or by rapidly stirring the fermentation mixture. If desired, a combination of stirring and the bubbling of air or oxygen can be used.

It is sometimes preferred to prepare the antibiotic substances by the use of the isolated 6-aminopenicillanic acid or one of the intermediate concentrates obtained during its isolation. A concentrated solution of G-aminopenicillanic acid can be prepared by evaporating the clarified harvest brew at reduced temperature and pressure to a small volume. If desired, the penicillins present in the brew can be largely removed by extraction with an organic solvent such as butyl acetate at an acid pH. After neutralizing the liquid substantial amounts of impurities can then be precipitated by the addition of solvents such as acetone, methanol or ethanol. After separating such impurities the clear liquor may then be further concentrated to give a concentrated preparation.

The productionby the process of this invention of antibiotic material fromfermentation liquor having little or no antibiotic activity is clearly indicated if, before the addition of one of the chemical reagents hereinbefore specified to the fermentation liquor, the penicillins already present as a result of the fermentation reaction by which the fermentation liquor was obtained are removed. This removal can readily be achieved as indicated above by extracting the penicillins from the acidified fermentation liquor by means of an organic solvent, for example, butyl acetate, in which the penicillins are soluble. It will be seen from the examples below that in some instances a very .considerable increase in antibiotic activity was obtained as a result of the chemical modification of the fermentation liquor according to the process of this invention.

Thus, 6-aminopenicillanic acid was prepared and isolated as follows:

(a) A strain of Penicillium chrysogenum 5120C (obtained from Professor E. B. Chain, Istituto l periore di Sanita, Rome) was first grown on a glycerol-molasses agar slope for 7 days at 26 C. Sterile distilled water was then added and the spores washed off the surface of the culture to produce a spore suspension. About 10 mls. of this suspension were used to inoculate litres of seed medium in a -litre stainless steel stirred fermenter.

The seed medium contained 8% w./v. corn steep liquor, I

6% w./v. of dextrin and tap water, the pH being adjusted to 6.1 before sterilizing the fermenter and its contents. The tank was stirred at 500 rpm. with an air flow of 1 vol./vol./min. and maintained at 27 C. for 48 hours. A volume of 3.2 litres of the contents of this fermenter was then transferred aseptically into a 90-litre stainless steel fermenter containing 50 litres of fermentation medium consisting of peanut meal 3.0% w./v., 1actose 4.0% w./v., Na SO 0.1% w./v., CaCO 1.0% w./v. and tap water. The pH was adjusted to 7.2'before the fermenter and its contents weer sterilized. After inoculation the tank was maintained at 26-28" C. for 4 days and stirred at 600 rpm. by means of animpeller of 12.5 cms. diameter. Air bubbled through the tank at the rate of 1 vol./ vol./ min. Foaming was controlled by the periodic addition of lard oil containing 2% of octadecanol.

The brew obtained was clarified and .40 litres thereof was concentrated in vacuoto a volume of 4 litres. The pH was then adjusted to 3.0 and the precipitate which formed was removed bytc'entrifuging and the'clear liquor was extracted once with half its volume of butyl acetate.

The aqueous phase was separated and the pH adjusted to 7.5. 3 vols. of acetone was then added with stirring and the precipitate removed by centrifuging. The clear liquor was then concentrated to 2280 mls. and the pH adjusted to 7:0. It had a potency of 54 ,u/mgm. assayed as described below.

chloride,

The 6-aminopenicillanic acid was assayed by reacting a sample with phenylacetyl chloride and assaying the penicillin found by the cup plate method described by N. G. Heatley in Biochem. J., 38, 61 (1944) using B. subtilis as the bacterium. The purity of the preparation can then be expressed in units per mgm. (a/rngm.) of dry substance.

The potencyof pure 6-aminopenicillanic acid assayed by this method is 2750 n/mgm.

(b) 1200 mls. of the concentrate of potency 54 t/mgrn. were percolated through 200 gms. of Dowex I resin conditioned with hydrochloric acid. The column was washed with water and this wash was combined with the percolate. The assay of this solution proved it to contain 15% of the 6-aminopenicillanic acid applied. The column was then eluted with 0.05 N hydrochloric acid. The pooled active fractions of the eluate contained 81% of the original 6-aminopenicillanic acid, the solution assaying at 900 ,u/mgm. The eluate was then adjusted to pH 6.0 and concentrated to 25 mls. in vacuo, concentrated hydrochloric acid was added with stirring to bring the pH to 4.3 and the crystalline 6-aminopenicillanic acid then filtered off and washed with water followed by acetone, and then dried in vacuo. The yield was 1.0 gm. assaying at 2200 t/mgm. pure. Repeated precipitation of the crystalline material from neutral aqueous solution by the addition of hydrochloric acid gave a white crystalline solid of melting point 209-210 C. assaying at 2740 t/mgm. analyzing as follows: (Found: C, 44.6; H, 5.7; N, 13.1; S, 14.1%. C H O N S requires: C, 44.4; H, 5.6; N, 13.0; S, 14.8%).

PREPARATION OF DERIVATIVES OF 6-AMINO- PENICILLANIC ACID The procedure to be followed in preparing antibiotic substances from 6-aminopenicillanic acid depends largely upon the extent to which the starting material has itself been purified. Thus, 6-aminopenicillanic acid may be used in three different stages of purification, as indicated below:

(a) From isolated 6-amin0penicilla'nic acid.--When 6- aminopenicillanic acid is available in relatively pure form it is only necessary to use a small excess (ca. 20%) of reagent and the product is, in turn, obtained fairly pure (asindicated by manometric assay using penicillinase).

The reagents used in this way include fifteen different monocarboxylic acid chlorides and also adipyl chloride, propionic anhydride, carbobenzoxyglycine ethoxy-formic anhydride, benzyl chloroformate, and p-toluenesulphonyl chloride. v

(I2) From 6-rzminopenicillanic acid concentrates..-The starting material was a clarified fermentation liquor which has been subjected to an initial concentration procedure and from which the natural penicillins had been substantially removed by solvent extraction at pH 2 to 3. The

[neutralized aqueous solution usually contained 0.6-1.2

larger excess of reagent 10'to 50 times the theoretical amount) because various impurities (e.g. amino-acids and simple peptides) would also be susceptible to acylation and similar reactions. The products were worked up in essentially the same way as-in (a), but the resulting sodium salts were, of course, very much lesspure.

The reagents used in this way include phenoxyacetyl phenylacetyl chloride, a-chlorophenylacetyl chloride, chloroacetyl chloride, diphenylacetyl chloride, and adipyl chloride (all of which had also been reacted by Method (a)) and also a-naphthylacetyl chloride, 43- naphthoxyacetyl chloride and p-nitrophenoxyacetyl chloride.

(c) From dilute brew.The initial material was the original clarified fermentation brew from which natural penicillins had been substantially removed by solvent extraction at pH 2 to 3, but which had not been concentrated. It was thus about ten times more dilute than the solutions used in Method (b). Use of a large excess of reagent was again essential. With this very dilute material no attempt was made to isolate the reaction products, but the formation of antibiotic material was demonstrated by the increased antibacterial activity of the solution after reaction and by paper chromatography, a new zone of biologically active material being detected in every case.

The reagents used successfully in this way include phenoxyacetyl chloride, phenylacetyl chloride, a-naphthylacetyl chloride, a-naphthoxyacetyl chloride, fi-naphthoxyacetyl chloride, p-nitrophenoxyacetyl chloride, a-chlorophenylacetyl chloride, diphenylacetyl chloride, crotonyl chloride, chloroacetyl chloride, phthalimidoacetyl chloride, benzoyl chloride, hexahydrobenzoyl chloride, m-sulphobenzoyl chloride, adipyl chloride, propionic anhydride, and n-butyric anhydride.

Two typical procedures are illustrated in detail as performed with phenoxyacetyl chloride to produce the known penicillin V, thus:

Procedure A Parts by weight Water 100 Corn steep liquor 8 Liquid glucose 6 and the pH of the medium had been adjusted to a value of 5.2-5.3 by th addition of a solution of sodium hydroxide. The liquid glucose used was a mixture of carbohydrates consisting essentially of maltose, glucose and low molecular weight dextrins. The inoculated flask was shaken for 48 hours at a constant temperature of 26 C. on a rotary shaking machine having a throw of 3.4 cm. and operating at 250 r.p.m. At the end of this period of 48 hours a substantial growth of mycelium had been obtained in the flask. The resulting culture was then used to inoculate a synthetic fermentation medium without the addition of an added procursor. The fermentation medium used had the following composition:

Parts by weight Water 100.0 Lactose 4.0 Glucose 2.0 Ammonium lactate 0.5 Ammonium acetate 0.3 KH PO 0.3 Na SO T-- FeSO -7H O 0.01 MgSO -7H 0.025 ZnSO -7H 0 0.002 MnSO, 0.002 CaCl CuSO -H O 0.0005 caco 1.0

The pH of the fermentation medium was about 6. The fermentation was carried out in a flask on a shaking machine at 26 C.

At the end of the 96 hours fermentation period, the mycelium obtained was filtered from the fermentation broth and fermentation liquor obtained as the filtrate was 8 acidified to pH 3 with phosphoric acid and extracted once with half its volume of butyl acetate at 5 C. which removed most of the penicillins which it contained.

The extracted fermentation liquor was neutralized with sodium hydroxid solution and assayed by means of the cup plate method described by N. G. Heatley in Biochem. J., 38, 61 (1944), using B. .rubtilis as the bacterium.

A 50 ml. portion of the extracted fermentation liquor was brought to pH 8 by the addition of solid sodium bicarbonate and stirred at 0 C. while a solution of 0.5 gm. of phenoxyacctyl chloride in acetone was added in the course of a few minutes. The mixture was stirred at 0 C. for the one hour, filtered, and excess reagent was re moved by extraction with three portions of ether. The ether extracts were themselves washed with water and the washings added to the main aqueous solution which was then readjusted to pH 6 to 7 by the addition of hydrochloric acid.

Assay of the aqueous solution obtained (which had a volume of 65 ml.) using the method referred to above, showed that it contained a material having considerable antibiotic activity which was about 11 times greater for the whole volume of liquid than that of the initial solution. The results obtained from the assay were as follows:

Activity (International units) Extracted fermentation liquid (volume 50 ml.) 650 Reaction product (volume 65 ml.) 7,150

By means of paper chromatography it was shown that the antibiotic material contained in the aqueous solution had an Rf value of the same order as penicillin V and the stability of the aqueous solution at pH 2 also indicated a resemblance to that of penicillin V.

Procedure B This procedure is typical of the reaction of isolating 6-aminopenicillanic acid with monocarboxylic acid chlorides.

A solution of phenoxyacetyl chloride (360 mgm.) in dry acetone (5 ml.) was added dropwise during 10 minutes to astirred solution of 6-aminopenicillanic acid (450 mgm., approximately 75% pure) in 3% aqueous sodium bicarbonate (18 ml.) and acetone (12 ml.). When addition was complete the mixture was stirred at room temperature for 30 minutes and then extracted with ether (30 ml. in 3 portions), only the aqueous phase being retained. This aqueous solution was covered with butanol (5 ml.) and adjusted to pH 2 by the addition of N hydrochloric acid. After separating the layers, the aqueous phase was extracted with two 2.5 ml. portions of butan01, adjusting to pH 2 each time. The combined butanol solutions (which at this stage contained the free penicillin acid) were washed with water (3 x 2 ml.) and then shaken with water (10 ml.) to which sufficient 3% sodium bicarbonate solution was added to bring the aqueous phase to pH 7. The butanol solution was further extracted with two 5 ml. portions of water to each of which was added enough bicarbonate solution to produce an aqueous phase at pH 7. The combined aqueous solutions were washed with ether (20 ml.) and then evaporated at low temperature and pressure to leave the crude sodium salt of phenoxymethyl penicillin which, after drying in a vacuum desiccator, was obtained as a slightly hygroscopic powder (591 mgm.).

The purity of the product was estimated by the penicillinase assay as 73% and, by bioassay, as 68%. In its chromatographic behaviour and its antibacterial spectrum the product showed no significant difference from authentic phenoxymethyl penicillin. It also exhibited the relative stability towards acids which is characteristic of this particular penicillin. No loss of activity could be detected after 2 hours at pH 2.

The following examples will serve to illustrate this invention without limiting it thereto:

EXAMPLE 1 The sodium salt of chloromethylpenicillin was obtained by repeating the process of Procedure B but using chloroacetyl chloride instead of phenoxyacetyl chloride. The yield of crude sodium salt (purity 77%) was 79 mgm. per 100 mgm. of 6-an1inopenicillanic acid. The percentage remaining after two hours at pH 2 was 80%.

The product inhibited the growth of E. coli at a concentration of 1 in 20,000, of P. vulgaris at a concentration of 1 in 4,000, of S. typhi at a concentration of 1 in 80,000, of Staph. aureus at a concentration of 1 in 4,000,- 000 and of B. subtilis at a concentration of 1 in 800,000.

EXAMPLE 2 The sodium salt of dichloromethylpenicillin was obtained by repeating the process of Procedure B but using dichloroacetyl chloride instead of phenoxyacetyl chloride. The yield of crude sodium salt (purity 31%) was 80 mgm. per 100 mgm. of 6-aminopenicillanic acid. The percentage remaining after two hours at pH 2 was 100%.

The product inhibited the growth of E. coli at a concentration of 1 in 16,000 of P. vulgaris at a concentration of 1 in 4,000, of S. typhi at a concentration of 1 in 80,000, of Staph. aureus at a concentration of 1 in 8,000,000 and of B. subtilis at a concentration of 1 in 1,600,000.

EXAMPLE- 3 The sodium salt of bromomethylpenicillin was obtained by the process of Procedure B but using bromoacetyl chloride instead of phenoxyacetyl chloride. The yield of crude sodium salt (purity 69%) was 107 mgm. per 100 mgm. of 6-aminopenicillanic acid. The percentage remaining after two hours at pH 2 was 95% The product inhibited the growth of E. coli at a concentration of 1 in 1,600, of P. vulgaris at a concentration of 1 in 1,600, of S. 'typhi at a concentration of 1 in 40,000, of Staph. aureus at a concentration of 1 in 2,000,000 and of B. subtilis at a concentration of 1 in 1,600,000.

EXAMPLE 4.-PREPARATION OF a-CHLOROPENTYL- PENICILLIN A solution of a-chlorohexoyl chloride (33 8 mg.) in dry acetone (2 ml.) was added dropwise during 10 minutes to a stirred solution of G-aminopenicillanic acid (433 mg, approx. 70% pure)in a 3% aqueous sodium bicarbonate (17 m1.) and acetone (13 1111.). When addition was complete the mixture was stirred at room-temperature for 1 hour and then extracted with ether (30 ml. in 3 portions), only the aqueous phase being retained. This aqueous solution was covered with butanol ml.) and adjusted to pH 2 by the addition of N hydrochloric acid. After separating the layers, the aqueous phase was extracted with two 2.5 ml. portions of butanol, adjusting to pH 2 each time. The combined butanol solutions (which at this stage contained the free penicillin acid) were washed with water (3 x 2 ml.) and thenshaken with water ml.) to which suflicient 3% sodium bicarbonate was added to bring the aqueousphase to pH 7. The butanol solution was further extracted with two 5 ml. portions of water to each of which was added enough bicarbonate solution to produce an aqueous phase of pH 7. The combined aqueous solutions were washedwith ether (20.ml.) and then evaporated at low temperature and pressure to leave the crude sodium salt of a-chloropentylpenicillin which, after drying in a vacuum desiccator, was obtained as a pale yellow powder (219 mg). It was estimated by m-ano-metric assay to be 77% pure. Thestability towards acids is indicated by the fact that 92% of the penicillin remained unchanged after a solution at pH 2 had been 10 kept for 1 hour at 35 C The penicillin inhibited Staph. aureus at a concentration of 0.012 meg/ml.

EXAMPLE 5.PREPARATION OF a-CHLOROHEPTYL- PENICILLIN 6-arninopenicillanic acid (216 mg., about 70% pure) was treated with DL-a-c'hloro-octoyl chloride (197 mg.) as described in Example 4. The final yield of crude sodium salt of a-chloro-heptylpenicillin was 157 mg., and this was estimated by manometric assay to be 61% pure. The percentage remaining after 1 hour at pH 2 and 35 C. was 79%. The penicillin inhibited Staph. aureus at a concentration of 0.006 mcg./ ml.

EXAMPLE 6.-PREPARATION 0F a-CHLOROBUTYL- PENICILLIN A solution of DL-a-chlorovaleric acid (233 mg.) and triethylarnine (0.25 ml.) in dry acetone (8 ml.) was stirred and cooled to -l0 C. A solution of ethyl chlorocarbonate (0.16 ml.) in dry acetone (4 ml.) was added dropwise over 10 minutes with continued cooling and stirring and after a further 40 minutes the precipitated triethylamine hydrochloride was removed. The cold filtrate (which contained the mixed anhydride) was added slowly to a stirred solution of 6-aminopenicillanic acid (300 mg, approx. 75% pure) in a mixture of 3% sodium bica1 bonate solution (8 ml.) and acetone (4 ml.) which had been previously cooled below -10 C. The mixture was stirred while it attained room temperature, and then for 2 hours more. The penicillin was isolated by extracting an acidified solution with butanol and then re-extracting the product into aqueous sodium bicarbonate as described in Example 4. The crude sodium salt of a-chlorobutylpenicillin was finally obtained as a slightly deliquescent straw-colored powder (410 mg), estimated by manometric assay to be 58% pure. The percentage remaining after 1 hour at pH 2 and 35 C. was 82%.

The penicillin inhibited Staph. aureus at a concentration of 0.012 meg/ml. E

EXAMPLE 7.-PREPARATION OF a-BROlllO-ISO-BUTYL- [PENICILLIN A mixed anhydride was prepared from a bromo-isovaleric acid (400 mg.) and ethyl chlorocarbonate (0.21 ml.) and allowed to react with G-aminopenicillanic acid (432 mg, approx. pure) as described in Example 6. The reaction mixture was worked up as previously described to give the crude sodium salt of a-bromo-iso butylpenicillin (839 mg), which was estimated by manometric assay to be 60% pure. The percentage remaining after 1 hour at pH 2 and 35 C. was The penicillin inhibited Staph. aureus at a concentration of 0.5 mcg./ ml.

EXAMPLE I8.PREPARATION OF aBROMOETHYL- PENICILLIN A mixed anhydride was prepared from DL-a-bromopropionic acid (370 mg.) and ethyl chlorocarbonate (0.21 ml.) and allowed to react with pure 6-aminopenicillanic acid (432 mg.) as described in Example 6. The reaction mixture was worked upon as previously described to give the crude sodium salt of ot-brornoethylpenicillin (3.90 mg.) which was estimated by manometric assay to be 56% pure. The percentage remaining after 1 hour at pH 2 and 35 C. was 89%. v

This product inhibited Staph. a ureus at a concentration of 0.1 pgJml.

EXAMPLE 9.-PREPARATION OF a-BROMOPENTYL- TENICILLI'N This-product is the same as that of Example 12. The present procedure is typical of the reaction of 6-aminopenicillanic acid with an ot-halogenoacid bromide.

A solution of DL-a-bromohexoyl bromide (5.1 g.) in dry acetone (30 ml.) was added dropwise during ,10 minutes to a stirred solution of 6-aminopenicillanic acid (3.9 g.) in water (65 ml.) containing sodium bicarbonate (4.5 g.) and acetone (35 ml.). When addition was complete the mixture was stirred at room temperature for 2% hours and then extracted with ether (2 x 65 ml.), only the aqueous phase being retained. This aqueous solution was covered with butanol (15 ml.) and adjusted to pH 2 by the addition of N hydrochloric acid. After separating the layers, the aqueous phase was extracted with two further portions of butanol (15 ml., then 7.5 ml.), adjusting to pH 2 each time. The combined butanol extracts were washed with water (2 x 20 ml.) and then shaken with N aqueous sodium bicarbonate solution (20 1111.). Evaporation of the resulting mixture at low temperature and pressure left the crude sodium salt of a-bromopentylpenicillin as a white powder (5.0 g.), which was estimated by manometric assay to be 60% pure. The percentage remaining after 1 hr. at pH 2 and 35 C. was 92%.

This product inhibited Staph. aureus at a concentration of 0.002 ,LLg./II11.

EXAMPLE 10 a-Chlorocaproic acid (2.09 gm., 0.0139 mole) was dissolved in a mixture of 30 ml. pure, dry dioxane, 6 ml. dry acetone and 1.95 cc. (0.0139 mole) triethylamine. After cooling to C. there was added isobutyl chloroformate (1.82 cc., 1.89 gm., 0.0139 mole) and the mixture was stirred for one hour at 0-5 C. To this mixture in the cold with stirring there was then added at 0 C. a solution of 6-aminopenicillanic acid (3.00 gm., 0.0139 mole) and triethylamine (1.95 cc., 0.0139 mole) in 30 ml. distilled water. After stirring one hour, there was added 30 ml. cold water and 1.0 g. NaHCO and the mixture was extracted with two 75 cc. portions of cold ether, which was discarded. The aqueous solution was then covered with 75 ml. ether, cooled and stirred in an ice bath and acidified to pH 2 with 6 N hydrochloric acid. The two phases were separated rapidly and an additional extraction was performed with 75 ml. cold ether. The combined ethereal extracts containing the product, 6-(2-chlorocaproamido)penicillanic acid, were washed with 25 ml. water, dried quickly over anhydrous Na SO and filtered. The addition of 12.5 cc. of dry n-butanol containing 0.373 gm./ml. potassium 2-ethylhexanoate converted the product to its potassium salt, which was precipitated by the addition of 300 ml. dry ether as a colorless gum which solidified upon trituration with 450 m1. ether and was collected, dried in vacuo over P 0 at 25 C. and found to weigh 4.15 gm., to be very soluble in water, to contain the ,B-lactam group'as shown by infrared analysis, to inhibit Staph. aureus Smith at a concentration of 0.078 meg/ml., to exhibit versus S. aureus Smith upon intramuscular injection in mice, a CD of 1.2 mgm./kg., to be resistant to penicillinase and to be only 13% decomposed by pH 2.5 acid under conditions which decomposed benzylpenicillin to the extent of greater than 99.5%, i.e. in 0.75 molar aqueous citric acid for one hour at 37 C.

EXAMPLE 11 2-Bromo-n-butyric acid 1.67 gm., 1.06 ml., 0.01 mole), triethylamine (1.54 ml., 0.011 mole) and isobutyl chloroformate (1.31 ml., 0.01 mole) were dissolved in 20 ml. anhydrous dioxane at 3-5 C. and stirred for 30 minutes. To this solution at 35 C. Was added a solution of 6- aminopenicillanic acid (2.16 gm., 0.01 mole) and triethylamine (1.4 ml., 0.01 mole) in 20 ml. water. The reaction mixture was stirred one hour at 3-5 C., adjusted to pH 8, and washed with ether. The aqueous phase was then covered with ether, acidified with 1:5 dilution H 80; and twice extracted with ether. The combined ethereal extracts containing the product, 6-(2- bromobutyramido)penicillanic acid, were washed with water, dried over anhydrous Na SO and filtered. Addition of 5 m1. dry n-butanol containing 0.373 gm./ml. potassium 2-ethylhexanoate precipitated the potassium salt of the product as a gummy oil which solidified on trituration with ether and was collected, dried overnight in vacuo over P 0 and found to melt at l78-18l C. (d.), to contain a fl-lactam ring by infrared analysis, to be soluble in water, to inhibit Staph. aureus Smith at a concentration of 0.078 mcg./ml. and to be resistant to penicillinase.

EXAMPLE 12 a-Bromo-n-caproic acid (2-bromo-hexanoic acid, 2.21 gm., 0.0139 mole) and triethylamine (2.0 cc., 0.0143 mole) were dissolved in 30 ml. dry dioxane and 6 ml. acetone. After cooling to 0 C., isobutyl chloroformate (1.82 cc., 0.0139 mole) was added and the mixture was stirred thirty minutes at 0 C. To this solution there was then added at 0 C. a solution of 6-aminopenicillanic acid (3.00 gm., 0.0139 mole) and triethylamine (2.0 cc.) in 30 ml. water. The mixture was stirred one hour; carbon dioxide evolution had essentially ceased after forty minutes. Ice water (30 ml.) containing 1.0 gm. NaHCO was added and the mixture was twice extracted with 75 ml. portions of ether, which were discarded. The aqueous phase was covered with 75 ml. ether in an ice bath, stirred and acidified to pH 2 with mineral acid. The ether was sepaarted and the aqueous phase was again extracted with 75 m1. ether. The combined ethereal extracts containing the product, 6-(2-bromocaproamido)- penicillanic acid, were washed with 25 m1. cold water, dried briefly over anhydrous Na SO and filtered. Addition to the ethereal solution of 12.5 ml. dry n-butanol containing 0.373 gm./ml. potassium 2-ethylhexanoate followed by addition of 500 ml. dry ether precipitated the potassium salt of the product as an oil which was triturated with 300 ml. ether and then 300 ml. lower alkanes (Skellysolve B) to give a hard gum. On drying the product about 19 hours in vacuo it was obtained as an amorphous white powder weighing 4.75 gm. It was very soluble in water and inhibited Staph. aureus Smith at a concentration of 0.15 meg/ml. and was only 14% decomposed by pH 2.5 acid under conditions which decomposed benzylpenicillin to the extent of greater than 99.5%.

EXAMPLE 13 A 0.020 mole run was carried out according to the procedure of Example 10 except that the a-chlorocaproic acid therein was replaced by 2.86 gm. (0.020 mole) 2,2- dichloropropionic acid to give 6-(2,2-dichloropropionamido)penicillanic acid which was isolated as the tan, crystalline potassium salt, 3.13 gm., M.P. 162-163" C. (d.),,containing the fl-lactam group as shown by infrared analysis and inhibiting Staph. aureus Smith at a concentration of 0.62 meg/ml. This salt was highly resistant to penicillinase and was only 2% decomposed by pH 2.5 acid under conditions which decomposed benzylpenicillin to the extent of greater than 99.5%.

EXAMPLE 14 A 0.00926 mole run was carried out according to the procedure of Example 11 except that the 2-bromo-nbutyric acid therein was replaced by 0.91 gm. (0.00926 mole) difluoroacetic acid to give 6-(2,2-difluoroacetamido)penicillanic acid which was isolated as the white, powdered potassium salt, 1.75 gm., M.P. -195 C. (d.), containing the fl-lactam group as shown by infrared analysis and inhibiting Staph. aureus Smith at a concentration of 0.62 meg/ml.

EXAMPLE 15 A solution was formed at 0-3 C. by mixing u-bromoisovaleric acid (5.45 g., 0.03 mole), triethylamine (4.22 ml., 0.03 mole) and isobutyl chloroformate (3.9 ml., 0.03 mole) in 40 ml. p-dioxane and 10 ml. acetone and was then stirred 20 minutes. A solution at 0-3 C. of 6-aminopenicillanic acid (6.51 g., 0.03 mole) and triethylamine (4.22 ml., 0.03 mole) in 40 ml. "water was 13 added to the first solution and the reaction mixture was stirred for one hour, adjusted to pH 8 with 10% aqueous sodium bicarbonate and extracted with ether, which was discarded. The aqueous phase was covered with ether, acidified to pH 2 with 6 N HCl and extracted twice with ether. The combined ethereal extracts containing the product 6 (a bromo iso valeramido)penicillanic acid, were washed with water, dried over anhydrous Na 'SO and filtered. Addition of 5 ml. (15 m1. would have been preferable) of 40% potassium Z-ethylhexanoate in dry n-butanol precipitated the potassium salt of the product as an oil which stiffened to a gum on trituration with ether and was dried over P in vacuo to yield 5.4 g. as a light fiuffy powder which decomposed above 128 C., contained the fi-lactam ring as shown by infrared analysis, was soluble in Water and inhibited Staph. aureus Smith at a concentration of 0.1 mcg./rnl.

EXA'MPLE 1 (3 Potassium 6-(dichloroacetamido)penicillanate (9 g.) was prepared from 6.8 g. dichloroacetyl chloride and 10 g. 6-aminopenicillanic acid and found to be soluble in water, to contain the 5-lactam group as shown by infrared analysis, to inhibit Staph. aureus Smith at a concentration of 0.2 meg/ml. to be resistant to penicillinase and to be not decomposed by pH 2.5 acid under the conditions shown above which decomposed benzylpenicillin to the extent of greater than 99.5%.

We claim:

1. A member selected from the group consisting of an acid having the formula wherein X represents an alpha-chloroalkanoyl group comprising from two to twenty-two carbon atoms inclusive.

3. 6-(zx-chloroacetamido)penicillanic acid. 4. 6-(tx,ot-dichloroacetamido)penicillanic acid. 5. 6-(ot-chloro-caproamido)penicillanic acid. 6. 6-(a-b romo-caproamido) penicillanic acid.

7. 6-(a-chloro-iso-valeramido)penicillanic acid.

References Cited in the file of this patent UNITED STATES PATENTS 2,479,296 Behrens et al. Aug. 16, 1949 2,479,297 Behrens et a1 Aug. 16, 1949 2,934,540 Sheehan Apr. 2 6, 1960 2,941,995 Doyle et a1 June 21, 1960 FOREIGN PATENTS 569,728 Belgium Nov. 15, 1958 

1. A MEMBER SELECTED FROM THE GROUP CONSISTING OF AN ACID HAVING THE FORMULA 